Conventional microwave UV irradiation systems include a magnetron and UV bulb combination. Upon the application of power, the magnetron generates radio frequency (hereinafter “RF”) energy to excite the gas of the UV bulb, which causes the UV bulb to emit UV energy. The emitted UV energy can be applied to various applications. For example, the UV energy can be applied to a substrate or product for curing materials thereon. In this way, materials, such as inks or adhesives for example, may be cured onto the various substrates or products by application of the UV energy produced by the UV bulb. As another example, the UV energy can be directed to a substrate or product to thereby modify the surface thereof.
Several different types of UV bulbs are known, each being designed with various chemicals to produce a greater amount of UV energy at select light frequencies. For example, a UV bulb with both Mercury and Iron will produce greater UV energy in the UVA wavelength range (320-390 nm), and a UV bulb with Mercury and Gallium will produce greater UV energy in the UVV wavelength range (390-460 nm). Furthermore, the power level in which a UV bulb is operated also affects the amount and spectral content of the UV energy radiated therefrom. In general, the most suitable type of UV bulb and the power level at which it should be operated depends on the application. Hence, to facilitate their usefulness, some microwave UV irradiation systems are able to operate several different types of UV bulbs at various power levels, such as the COOLWAVE 2610, COOLWAVE 2 510, and COOLWAVE 2 410 developed by the Nordson Corporation.
It is also well known for microwave UV irradiation systems to include a cooling device, which is used to cool both the magnetrons and the UV bulb to keep them from exceeding acceptable operating temperatures. Conventional cooling systems use a fixed air pressure value and a pressure sensor to infer the flow of cooling air to the magnetrons and the UV bulb, regardless of the UV bulb type and power level being used. In other words, the cooling system adjusts the air flow based on a comparison between a pressure sensor reading and the fixed air pressure, and the fixed air pressure remains the same across all the various UV bulb types and power levels. However, depending on the UV bulb type and the power level being used, different degrees of cooling are necessary because some UV bulbs reach higher operating temperatures than others. For this reason, the fixed air pressure value and pressure sensor used to infer air flow in conventional systems is problematic. More particularly, as the temperature of a UV bulb decreases, the amount of UV energy that is radiated from the bulb tends to decrease, especially when the UV irradiation system is being operated at less than full power. In addition, if a UV bulb is over-cooled, the spectral content of the emitted UV energy may change, which is known as spectral shifting. Therefore, because the various UV bulb type and power level combinations require different degrees of cooling, as mentioned above, cooling based on achieving the fixed air pressure value as implemented in conventional systems may result in cooling some UV bulbs more than is necessary, thereby causing an unnecessary decrease of the amount of radiated UV energy or spectral shifting.
For these reasons, as well as others, it would be desirable to provide a system, method, and computer program product to improve blower cooling control and thereby optimize the amount of UV energy that is emitted by the various types of UV bulbs operating at various power levels, as well as prevent spectral shifting.